In an on-board emergency reporting apparatus disclosed in US 2004/0075345 corresponding to JP-A-2000-322677, a power source for supplying operating power to the emergency reporting apparatus switches from a vehicle battery device to an auxiliary battery device when a voltage level of the vehicle battery device drops, for example, during engine starting. Thus, even when a trigger event for an emergency reporting procedure occurs during a period of time when the voltage level of the vehicle battery device is low, the emergency reporting apparatus can perform the emergency reporting procedure.
In another on-board emergency reporting apparatus disclosed in JP-A-2000-222659, if operating power supplied from a vehicle battery device to a power supply circuit of the emergency reporting apparatus is interrupted when a trigger event for an emergency reporting procedure occurs, the power supply circuit automatically switches from the vehicle battery device to an auxiliary battery device to receive the operating power from the auxiliary battery device.
In such conventional emergency reporting apparatus, the following problems may arise. If the power supply circuit remains instructed to receive the operating power from the auxiliary battery device even after completion of the emergency reporting procedure, the auxiliary battery device remains discharged. For example, when the auxiliary battery device is replaced with new one for the next emergency reporting procedure, the new auxiliary battery device is wastefully discharged. For further example, when the auxiliary battery device is continuously used without being replaced with new one, the charged of the auxiliary battery device is reduced to an insufficient level for the next emergency reporting procedure.